The present invention relates to a wicking aramid fabric formed from crystallized yarns for use in firefighter turnout gear and other protective apparel.
Several recent patents, including U.S. Pat. Nos. 5,323,815; 5,499,663 and 5,539,928 have taught the advantage of using a multifilament fabric for the inner lining of fire fighter turnout gear. Such multifilament yarn fabrics, in contrast to staple yarn fabrics, provide a more slippery fabric surface which increases the flexibility and mobility of garments and increases the ease of movement of the fire fighter as he or she works while wearing the garment.
Although wearer comfort is improved by the use of such multifilament fabrics as the inner lining or as a facing for other fabric layers of the turnout gear, multifilament yarn fabrics, in contrast to staple or spun yarn fabrics, have poor water wicking properties. And although the fire fighter can move with more comfort because the multifilament yarn fabric offers less resistance to movement, moisture and perspiration produced by the fire fighter""s own metabolism builds up on the skin since it is not wicked away by the filament yarns in contact with the skin. The fire fighter becomes uncomfortable, and the fire fighter""s wet skin surface aggravates the ease of movement that the garment was designed to achieve.
All fabrics used in the construction of fire fighter protective clothing must pass minimum performance requirements for resistance to flame, heat and tearing. Thus the inner lining of protective garments designed for fire fighters and garments designed for others who work in environments where there is a danger of exposure to flame and high temperature are usually made from aramid fibers and yarns. Most often these aramid yarns and fibers used in the construction of protective clothing have been subjected to a hot stretching operation in manufacture to fully develop fiber mechanical properties. Such fibers and yarns are substantially, if not fully, crystallized.
It is well known in the art that m-aramid crystallized or substantially crystallized yarns and fabrics have closed surfaces and are difficult to dye or otherwise size or treat with yarn or fabric finishes. For example, U.S. Pat. No. 5,096,459 teaches that it is necessary to treat crystallized m-aramid yarns or fabrics with steam at a temperature of at least 120xc2x0 C. for about 15 minutes in order for water soluble dyes and carrier, padded on these fibers and yarns to be absorbed.
U.S. Pat. No. 4,755,335 taught that even treatments applied to never dried m-aramid yarns and fibers required contact with steam at a temperature of from 110 to 140xc2x0 C. for adequate absorption of the treatment to take place.
U.S. Pat. No. 4,525,168 teaches that it is necessary to swell the crystallized m-aramid fabric or yarn by immersing the fabrics or yarns in a solvent such as dimethyl formamide, dimethyl sulfoxide or dimethyl acetamide for a period of 30 minutes in order to open the yarn surface so that a dye site may be introduced and the crystallized polymer may be successfully dyed.
The object of the present invention is to provide a wicking, crystallized yarn, aramid fabric for use in protective clothing including fire fighter turnout gear and other types of protective clothing. Another object of the present invention is to provide a process for making such a fabric.
The present invention is a wicking fabric comprising aramid crystallized yarns, and in particular the fabric of the present invention is comprised of 75% by weight or more aramid crystallized yarns.
The aramid crystallized yarns used in the present invention are staple yarns, multifilament yarns or mixtures of staple and multifilament yarns and are formed from m-aramid, p-aramid or mixtures of m- and p-aramid fibers. It is preferred that the major component of the fabric of the present invention is m-aramid yarn.
The fabric of the present invention is particularly useful in a protective and is a preferred fabric for a garment that is fire fighter turnout gear comprising an outer shell, a moisture barrier and a thermal barrier.
The garment of the present invention includes protective coats or overalls.
The present invention also includes a process for making a wicking fabric wherein the fabric contains more than 75% aramid crystallized yarns comprising the steps:
(a) padding the fabric with a water solution containing from 10 to 800 grams per liter of polar solvent;
(b) allowing the solution to remain in contact with the fabric at room temperature for a time sufficient to swell the fibers of the fabric, but not more than 36 hours;
(c) padding the fabric with a solution of a wicking finish; and
(d) drying the fabric at a temperature not more than 200xc2x0 C. for a period of not more than 30 minutes.
Polar solvent useful in the present process are those selected from the group consisting of dimethyl acetamide, dimethyl formamide and dimethyl sulfoxide.
In the present process, it is preferred that padding is run at a pad pressure that results in a 1% to a 70% pick-up of solution based on the dry weight of the fabric. It is also preferred practice that before step (d) the padded fabric is kept from drying out. If the concentration of solvent remaining in fabrics treated according to the present method is of concern, the method may be run so that the final concentration of solvent in the fabric after drying is less than 1% by weight by:
(a) padding the fabric with a water solution containing about 25 grams per liter of polar solvent at a pad pressure that results in a 10 to 50% by weight pick-up of solution by the fabric;
(b) allowing the solution to remain in contact with the fabric at room temperature for about 16 hours;
(c) padding the fabric with a solution of a wicking finish; and
(d) drying the fabric at a temperature not more than 200xc2x0 C. for a period of not more than 30 minutes. Polar solvents for this method include those selected from the group consisting of dimethyl acetamide, dimethyl formamide and dimethyl sulfoxide. In this version of the present method, it is preferred that the padding is run at a pad pressure that results in a 1% to a 70% pick-up of solution based on the dry weight of the fabric. It is also the preferred practice that before step (d) the padded fabric is kept from drying out.